Because of our recent safety study of an Immune Globulin (IG) prepared from a c100-3 reactive plasma pool performed in a chimpanzee (see Z01 BQ 04006-99), we obtained two additional chimpanzees for assessing the presence of neutralizing antibodies in such an IG preparation enriched in antibodies to HCV. Two intravenous immunoglobulin preparations were used; the experimental contained high levels of antibodies to HCV envelope proteins, E1 and E2, while the control had little or no such antibodies. The experimental HCIGIV is an unlicensed product prepared by North American Biologicals, Inc. (NABI) from a plasma pool consisting of plasma from 198 anti-HCV positive donors and hence similar to our previous experimental HCIG. The control IGIV was a commercial IGIV product, Venoglobulin-S, which was prepared from large plasma donations all of which screened by the multiantigen EIA. Both preparations had been solvent-detergent treated in their manufacture and did not have detectable HCV RNA when assayed by our RT-PCR assay. The experimental chimpanzee was infused with a mixture consisting of 1 ml of a standard HCV inoculum (H-strain) containing 64 CID50 preincubated in vitro with 50 ml of 5% HCIGIV at 4 degrees C for 24 h while the control chimpanzee will receive the same CID50 inoculum preincubated with 50 ml of 5% Vinoglobulin-S under the same conditions. After 8 months of infusion, neither chimpanzee has yet had elevated alanine aminotransferase (ALT) (equal to or higher than 2.5 times of the basal value) in their weekly serum specimens. The study is still in progress. If HCIGIV contains neutralizing antibodies to HCV, the recipient chimpanzee should not contract HCV infection while the control should.